Polymerization catalyst

ABSTRACT

A process for preparation of a Ziegler-type catalyst having increased activity comprises admixing titanium tetrachloride, trihydrocarbyl aluminum and an ether, aging the mixture followed by addition of a dihydrocarbyl aluminum chloride prior to contact with the ethylenically unsaturated monomer to be polymerized.

La Heij et a1.

POLYMERIZATION CATALYST Inventors: Gerardus E. La Heij; Gerrit J. van

Amerongen, both of Amsterdam, Netherlands Foreign Application Priority Data Dec. 4, 1972 Great Britain 55860/72 U.S. Cl. 252/429 B, 260/943 Int. Cl C08d l/l4 Field of Search 252/429 B References Cited UNITED STATES PATENTS 10/1960 Geisler et al. 252/429 B X [451 Feb. 4, 1975 3,058,970 10/1962 B X 3,442,878 5/1969 B X 3,530,107 9/1970 Yoshioka et a1. .1 252/429 B X 3,580,899 5/1971 Massoubre 252/429 B X 3,676,416 7/1972 Makimoto 252/429 B X 3,709,851 l/1973 Mori et a1. 252/429 B X Primary Examiner-Patrick P. Garvin Attorney, Agent, or Firm-H. W. Haworth [57] ABSTRACT A process for preparation of a Ziegler-type catalyst having increased activity comprises admixing titanium tetrachloride, trihydrocarbyl aluminum and an ether, aging the mixture followed by addition of a dihydrocarbyl aluminum chloride prior to contact with the ethylenically unsaturated monomer to be polymerized.

11 Claims, No Drawings 1 POLYMERIZATION CATALYST BACKGROUND OF THE INVENTION It is known that ethylenically unsaturated monomers such as isoprene can be polymerized by means of an ether-modified Ziegler-type catalyst, e.g., a TiClJtrialkyl aluminum-based catalyst. The principal effects of the ether modifier are a reduction in gel content, and increase in molecular weight, an increase in swelling index and sometimes a slightly lower reaction rate. It has now been found that addition of a dihydrocarbyl aluminum chloride (R AICI) to such ether-modified TiCl catalysts enhances the activity thereof.

It is known that R AlCl is unsatisfactory in the preparation of TiCl catalysts by reduction of TiCL, for the polymerization of isoprene. At best isoprene will polymerize at a low reaction rate and with poor yields, and the product will have a poor microstructure. It has been suggested in US. Pat. No. 3,442,878 that RgAlCl, used to destroy impurities in the isoprene or the polymerization solvent, may improve the yield in the polymerization operation. It has now been found that R AlCl added to the aged catalyst results in an important gain in catalyst activity.

SUMMARY OF THE INVENTION The invention provides a process for the preparation of a TiCl catalyst having increased activity in the polymerization of isoprene, which comprises admixing TiCl trihydrocarbyl aluminum and an ether, thereafter aging the catalyst mixture thus obtained, and adding a dihydrocarbyl aluminum chloride to the aged catalyst mixture, prior to being brought into contact with isoprene. The invention also relates to a process for the polymerization of isoprene employing said catalyst.

DESCRIPTION OF PREFERRED EMBODIMENTS Examples of trihydrocarbyl aluminum (ALR compounds which may be used in the process according to the invention are trimethylaluminum, triisobutyl aluminum, trioctyl aluminum, tricyclohexyl aluminum, and mixtures thereof. Suitable trialkyl aluminum compounds in which the alkyl groups have 2-4 carbon atoms each, may be employed such as triethyl or triisobutyl aluminum, the latter compound being preferred.

Any organic ether may be used in the process according to the invention. Preferred ethers are those represented by the formula R--O-R', wherein R and R" can be the same or different alkyl, cycloalkyl, aryl or alkenyl groups. Thus diethyl ether, di-n-propylether, di-n-butyl ether, di-isoamyl ether, anisole, di-nhexylether, n-propyl phenyl ether, diphenyl ether and the like can be utilized. Di-n-butyl ether and diphenyl ether have been found to provide very good results.

The molar ratio of AIR; to TiCl, to be used in the preparation of the catalyst mixture can vary within the range of 0.8 to 1.2, preferably of 0.9 to 1.0. The molar ratio of the ether to TiCl can vary from about 0.01 to 10, preferably from about 0.1 to l.

The reaction between AlR TiCl and ether is 'suitably carried out in the presence of a diluent. Suitable diluents are aliphatic or cycloaliphatic hydrocarbons such as cyclohexane or isooctane and suitable concentrations of TiCl and AIR;, are in the range of 50 to 1,000 mmol/l. Titanium concentrations below 50 mmol/l may result in reduced activity due to insufficient reduction of TiCl The temperature at which the catalyst components (i.e., TiCl aluminum trihydrocarbyl and the ether) are admixed is preferably below 270K, and particularly in the range from about 200 to about 260K. Higher and lower temperatures may be used, if desired, though temperatures above 300K are less desirable.

The order of addition of the unaged catalyst components is essentially immaterial provided that TiCl, and the ether should not be initially admixed in the absence of AlR The AIR and TiCl, may be admixed whereupon the ether is added. Preferably, the ether is mixed with AIR, and the mixture added to the TiCl Some agitation is beneficial to development of high catalyst activity.

After admixing the catalyst components the catalyst mixture is aged. Although aging temperatures up to 370K may be employed, preferred temperatures are below 300K, and especially in the range from about 240 to about 260K. During aging a highly active catalyst composition is formed containing TiCl in the betamodification. The time required for this transformation is usually at least 10 minutes; aging periods from about 30 minutes to about 10 hours are preferred. Aging times of more than 10 hours are usually not beneficial to a further increase in catalytic activity. After aging at the preferred temperatures between 240 and 260K the temperature of the catalyst mixture may be raised up to 300K or higher which usually increases the catalytic activity still further. It should be remembered, however, that at temperatures above 270K the catalyst slowly deteriorates. Prolonged storage at temperatures above 270K is, therefore, to be avoided. Safe storage temperatures of aged catalyst mixtures are preferably below 250K.

After aging of the catalyst mixture but prior to contact with isoprene, a dihydrocarbyl aluminum chloride (AlR Cl) is added thereto. The hydrocarbyl groups in AlR Cl are preferably alkyl groups having 1 to 12 carbon atoms such as methyl, ethyl, n-propyl, isobutyl, n-hexyl, 2-ethylhexyl and dodecyl. It will be understood that the two hydrocarbyl groups in AlR Cl need not be the same. A preferred representative of AlR Cl is diethyl aluminum chloride.

The amount of AlR CI to be added to the aged catalyst mixture is generally such as to provide 0.05-2, preferably 0.1-0.5 mol of AIR CI per atom of titanium.

The AlR Cl is added to the catalyst mixture prior to the introduction of the monomer. In certain cases some interval of time, e.g., 5-60 minutes, may be useful before the catalyst is contacted with e.g., isoprene, especially when the concentrations of the catalyst mixture and AIRgCI are relatively low. The temperature at which AlR Cl and the catalyst mixture are admixed may be the same as the polymerization temperature. Generally speaking, suitable polymerization temperatures are between 250 and 390K and particularly between 270" and 320K.

Suitable catalyst concentrations in the reaction mixture during polymerization are usually below 20 milliatoms, preferably between 0.05 and 5 milliatoms of titanium per liter. It may be advantageous to add the catalyst incrementally on a continuous basis during the polymerization until near the point where the desired degree of conversion has been reached.

The polymerization is suitably carried out in a liquid diluent for which purpose the same diluents may be employed as used in the preparation of the catalyst mixture. Preferred diluents are isopentane, cyclohexane, toluene, and tertiary amylenes. The term tertiary amylenes describes a hydrocarbon mixture containing Z-methyl-l-butene, 2-methyl-2-butene and 3-methyl-l- 1 hour at 293K, aluminum dialkychloride (AlR Cl) was added immediately prior to polymerization. Comparative examples without AlR Cl added to the catalyst were also performed.

butene. The polymerization may be continued until 5 b. The polymerizations were performed in pressurepolyisoprene concentrations of e.g., 550%w, preferatight 500 ml bottles, half-filled with liquid, out of bly of l5-25%w in the diluent have been obtained. contact with oxygen and moisture. The polymerization Preferably isoprene is homopolymerized. Other disolvent was isopentane, the isoprene concentration enes such as piperylene may be present in small %w, and the titanium concentration 2 mmol/l. Polyamounts, e.g., less than 0.5%w based on total dienes. l0 merization was effected at 293K for 30 minutes. The Higher amounts tend to decrease the polymerization polymerization was stopped by addition of 0.1%w of rate and the cis-l,4 content as well as the molecular methanol, based on the mixture. After addition of weight of the polyisoprene. Butadiene may be present 0.2%w of a phenolic stabilizer (available under the in large amounts, e.g., 2%. The isoprene feed as well as trademark IONOX 330) based on polymer, the polythe diluent, may be purified by methods known in the 15 mer was recovered by steam stripping and drying under art, e.g., by distillation, treatment with a sodium dispervacuum at 325K. Results are shown in the following sion, percolation over a molecular sieve, and the like. table,

Experiment a b c d e f g h l 2 Ether/AlBu molar ratio 0 0 0 0 0.25 0.25 0.25 0.25 0.25 0.25

AlBu lTiCl molar ratio 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85 0.85

Al-diethylchloride,

mmol/l 0.5 (a) 0.5 (g) (d) 0.5

Al-di-isobutyl chloride,

mmol/l 0l5 0.5

Polymerization:

7t conversion of isoprene 45 65 l0 15 67 78 72 12 83 82 k, min-.10- l0 l7 2 3 1s 21 2 29 Hoekstra viscosity 42 34 nd nd 46 42 37 nd 36 32 LVN, dl/g 4.4 3.4 nd nd 4.0 4.2 3.4 Rd 4.1 3.5

76 cis-l.4 nd nd nd nd 99 99 nd nd 99 nd The following examples further illustrate the invenbased on liters polymerization mixture. tion but are not intended to limit the scope thereof. Catalyst activity has usually been indicated by percent Experiments a-h for comparison. in experiment fthe conversion in a given time, also by the polymerization Al-diethyl-chloride was added to the isoprene/isopenrate constant k. This constant was calculated from the t n ixture, conversion data according to the equation: 1 d not deter in d (Co/C1) K 1 #0), in which Co is the initial d. 0.1 mmol Altri-isobutyl/l added to catalyst mixprene concentration at timt t,,,(;, the isoprene concenture tration after a polymerization time 1 minutes and k is 5 g, 5 mmol Al-ethyi.ethoxy-chloride/1 added to the first-order polymerization rate constant in min". the catalyst mixture, The limiting Viscosity number was measured m A further comparative experiment was performed,

9 at 303 h Hoekstl'a vlscoslty was measured substantially under the conditions of experiment e, in at 373 K after loadmg the Speclme" for 30 Seconds which in addition to the aluminum triisobutyl, 0.05 with 0 98 MN/m as described in Proceedings Rubber moles of aluminum diethyl chloride per mole of TlCl, Technology collferencet London 1938 Page and was added in the preparation of the catalyst mixture. Rubber Plastics Age 42 (197]) 1079; The lsoprene conversion was 5%, the rate constant k 0.001 content was measured by Nuclear Magnetic Resonance i -l.

(NMR).

EXAMPLE 1 EXAMPLE II a. The catalyst was prepared from (1) a solution of k in iSOOCIahe and a miXtul'e 0f y ether Substantially as described in respect of the above exahd aluminum h'iisobutyl W!) in isooctahe- The periments l and 2, further experiments 3 and 4 were AlBu ether solution was added to the TiCl solution at 253!(. A titanium concentration of 50 mmol/l was employed. All operations were carried out under nitrogen with the exclusion of oxygen and moisture. After the catalyst mixture was aged for l hour at 253K and for made in which diphenyl ether was employed instead of di-n-butylether. After the catalyst mixture was aged aluminum diethyl chloride was added thereto in an amount equivalent to 0.5 mmol/l of polymerization mixture. Results are shown in the following table.

' a molar ratio of trihydrocarbyl aluminum to TiCl of Experiment 4 from about 0.8 to about 1.2, thereafter aging the cata- DiphenyletherlAlBu molar ratio 0.5 lyst mixture thus obtained, and adding from about 0.05 lsoprene coh version, 84 86 to about 2 moles ofa dihydrocarbyl aluminum chloride iv l 3 per atom of titanium to the aged catalyst mixture. prior Hoekstra viscosity 45 3 to being brought into contact with monomer.

2. A process as in claim 1 wherein the trihydrocarbyl aluminum employed is a trialkyl aluminum having alkyl EXAMPLE I11 [0 groups of 2-4 carbon atoms each. Substantially as described hereinbefore, experiments A F f m Glam 1 where, the molar rano of ether to T|Cl 18 from about 0.1 to about 1.0. were performed with dodecyl-4-tolylether (DTE) and e 4. A process as in claim 3 in which the ether 18 sedmonylether (DNE).

lected from the group consisting of di-n-butyl ether and I5 diphenyl ether. I 5. A process as in claim 1 in which the molar ratio of Expemnem 5 6 trihydrocarbyl aluminum to TiCl is between about 0.9 DTElAlBu molar ratio 0.5 and about DNE/AlBu molar ratio 0.25 6. A process as in claim 1 wherein the catalyst mixgg f i gslg gg f f 3' 2' ture is aged at a temperature between about 240K and k. min".l0' 3| 33 about 260 K.

7. A process as in claim 1 wherein the dihydrocarbyl aluminum chloride employed is a dialkylaluminum EXAMPLE W chloride, the alkyl groups having 1-12 carbon atoms Substantially as described in the previous examples, each. a number of polymerizations was effected in various 8. A process as in claim 7 wherein the dialkylalusolvents. In all cases a molar ratio between AlBu and minum chloride is diethylaluminum chloride. TiCl of O 85 wa em loyed. To the aged catalyst 0.5 9. A process as in. claim 1 wherein the amount of dimol/l of Al-di-ethylchloride was added. Further condihydrocarbyl aluminum chloride is from about 0.1 to tions and results are given in the following table. about 0.5 moles per atom of titanium.

Experiment 7 8 9 10 ll 12 13 l4 l5 Ether employed,

molar ratio ether/AlBm, Di-n-butylether 0.25 0.25 0.25 0.25 0.25 diphenylether 1.0 dinonylether 0.25 0.25 dodecyl-ltolylether 0.5 Polymerization: solvent used 1P 1P CH CH CH 1P 1P CH [P temperature "K 293 293 293 293 313 293 293 313 293 time, hours 0.5 2 0.5 2 0.5 0.5 2 0.5 lsoprene conversion, 83 91 87 95 83 86 85 85 84 IP isopcntune CH cyclnhexune What iS claimed i 10. The catalyst obtained by the process of claim 1. A Process for the Preparanon of Tlcla'based P 11. A process as in claim 1 wherein the admixing of lymerization catalyst having increased activity which consists essentially of admixing TiCh, trihydrocarbyl aluminum and ether having the formula R"O--R, wherein R and R are the same or different alkyl, cycloalkyl, aryl or alkenyl groups, in a molar ration of ether to TiC1 of from about 0.1 to about 10.0 and in TiCl trihydrocarbyl aluminum and the ether is carried out in the presence of an aliphatic or cycloaliphatic hydrocarbon diluent wherein the concentration of TiCl. and trihydrocarbyl aluminum is in the range of about 50 to about 1,000 mmol/l. 

2. A process as in claim 1 wherein the trihydrocarbyl aluminum employed is a trialkyl aluminum having alkyl groups of 2-4 carbon atoms each.
 3. A process as in claim 1 wherein the molar ratio of ether to TiCl4 is from about 0.1 to about 1.0.
 4. A process as in claim 3 in which the ether is selected from the group consisting of di-n-butyl ether and diphenyl ether.
 5. A process as in claim 1 in which the molar ratio of trihydrocarbyl aluminum to TiCl4 is between about 0.9 and about 1.0.
 6. A process as in claim 1 wherein the catalyst mixture is aged at a temperature between about 240*K and about 260*K.
 7. A process as in claim 1 wherein the dihydrocarbyl aluminum chloride employed is a dialkylaluminum chloride, the alkyl groups having 1-12 carbon atoms each.
 8. A process as in claim 7 wherein the dialkylaluminum chloride is diethylaluminum chloride.
 9. A process as in claim 1 wherein the amount of dihydrocarbyl aluminum chloride is from about 0.1 to about 0.5 moles per atom of titanium.
 10. The catalyst obtained by the process of claim
 1. 11. A process as in claim 1 wherein the admixing of TiCl4, trihydrocarbyl aluminum and the ether is carried out in the presence of an aliphatic or cycloaliphatic hydrocarbon diluent wherein the concentration of TiCl4 and trihydrocarbyl aluminum is in the range of about 50 to about 1,000 mmol/l. 